The objective of this study is to evaluate the efficacy of ibuprofen and diazepam alone and in combination, versus a placebo, in the short-term management of patients with the myofascial pain-dysfunction syndrome (MPD). Pain and mandibular function are assessed over a washout period (2 weeks) and treatment period (four weeks). Beta-endorphin levels and cortisol levels are being assessed from blood samples of these patients. The headache study looks at a similar population group with myogenic headache who have pain on a daily or near-daily basis plus muscle tenderness to palpation and limited range of motion in the cervical spine (due to spasm). The study compares non-drug therapy (exercise, home physical therapy) versus a drug combination (ibuprofen/diazepam) and a placebo drug. All arms of the study are balanced to give each group equal time and physician, and family attention. Pain, quantitative muscle tenderness (measured with a hand-held "algometer"), range of motion, and side effect data are collected by an independent, blinded evaluator.